Can Modern Agriculture Be Sustainable?: Perennial polyculture holds promise
Written by Beth Baker
In October, a flurry of news articles hailed the arrival of a new beer produced by Patagonia Provisions, an offshoot of the outdoor clothing company. Long Root Ale is the first beer to be made from Kernza, a perennial grain bred from intermediate wheatgrass (Thinopyrum intermedium) by the Kansas-based Land Institute.
Dubbed “an ecologist's dream” by a Washington Post food writer, Kernza is on the leading edge of a global effort to develop perennial crops as a way to make agriculture sustainable and to support ecological intensification. Plant geneticists, evolutionary biologists, agronomists, food scientists, and agroecologists are collaborating to develop perennial crops, among them rice, wheat, sorghum, pigeon pea, barley, and sunflowers. A 2013 United Nations Food and Agriculture Organization expert workshop on “Perennial Crops for Food Security” concluded, “As feeding 9 billion people in 2050 with increasingly scarce and degraded natural resources is the main challenge faced by humankind, reinvigorating agriculture in a sustainable and productive way on a large scale will take nothing short of a significant shift in agriculture as we know it.”
That effort has been the Land Institute's mission since it was founded in 1976. Its goal is to transform farming from annual monoculture to perennial polyculture. “We’re trying to develop an agriculture that functions more like the ecosystem that agriculture replaced,” says Tim Crews, director of research and lead scientist of the Land Institute's ecology program. “In order to develop that ecosystem, you need perennial crops. They are not the goal, per se, but a central component of a more functional ecosystem. That will include transformation of the soil microbiome, and it will involve numerous crop species on the landscape.”
For millennia, humans have bred plants to grow faster and have higher nutrient value. Agricultural production accelerated dramatically during the “Green Revolution” of the 1970s, with farmers urged to use chemical fertilizers and pesticides and to intensify the mechanization of planting and harvesting. Productivity rose at astonishing rates. Today, in the Midwest, rows of soybeans and corn dominate much of the landscape that was once prairie.
Perennial pigeon pea and polyculture.
In Malawi, Sieglinde Snapp, of Michigan State University, uses a participatory research approach to work with local farmers who plant perennial pigeon pea along with maize, the staple crop. “These mixtures fit well in the marginal areas,” says Snapp. “It's providing options to improve overall productivity along with these other ecological benefits. We’re looking at yield sustainability and quantifying environmental benefits under different conditions.”
The project, which is supported by the government of Malawi and USAID Africa RISING (Research in Sustainable Intensification for the Next Generation), allows scientists to use weather-station data linked up to crop modeling to develop extension recommendations for farmers. “The farmers are using perennial pigeon pea in polycultures, an approach we have systemized and are now testing at scale to see the impact on environmental properties across the landscape,” says Snapp.
Polyculture, as it turns out, has been practiced all along by many small farmers in Malawi. “It took a while to find them,” says Snapp. “We evaluate what farmers are actually doing. We’re discovering you can combine modern varieties of pigeon pea with these historic practices, and the combination makes it a lot more sustainable.”
“Modernizing was all about yields,” says Sieglinde Snapp, professor of soils and cropping systems ecology at Michigan State University, who leads a project to bring perennial grains to Africa (see the box at right). “If you just compare crops on yield, then you can’t beat fertilized corn. But if you also want green cover for the Earth and nitrogen fixation and clean water, you have to measure them and give the plant credit for that.” Agriculture, she argues, should be directed toward both ecological services and food production.
Kernza and other long-lived crops have much longer root systems than annuals do, allowing the plants to survive for several years without disturbing the soil. By planting perennial grains along with cover crops, such as alfalfa, farmers can reduce the need for tillage and for fertilizers and pesticides while fixing nutrients into the plants.
As Lee DeHaan, lead scientist of the Land Institute's Intermediate Wheatgrass Program, and colleagues noted in the August 2006 BioScience, “The superior capacity of perennial plants to store carbon, manage resources, and stop soil erosion is widely recognized among ecologists and soil scientists, yet in 2006, only a handful of plant breeders are working to develop perennial grain crops.”
The pace is now picking up, thanks to advances in genome sequencing and in understanding the role of the soil microbiome. Support has come from the Gates Foundation, the US Agency for International Development (USAID), dozens of research institutes, and others.
Also spurring the research in the Midwest is growing concern over change in climate and over water quality degradation, says Craig Sheaffer, professor of agronomy and plant genetics at the University of Minnesota who collaborates with the Land Institute. “In the last 10 years, the issue of carbon sequestration has become more important,” he says. “Likewise, in Minnesota, there has been much greater emphasis on water-quality issues.” State agencies have documented sediment loading of rivers from field runoff, and there are a growing number of wells and streams whose waters exceed federal drinking-water standards for nitrate.
How climate change might affect perennial polyculture, on one hand, and how perennial polyculture might help mitigate the adverse effects of a warmer, drier climate, on the other hand, are big questions. “We’re interested in how much carbon can be sequestered in a perennial grain system,” says Crews. “There are all sorts of approaches people talk about to mitigate atmospheric carbon dioxide with land-use changes…. Most tilled lands have lost between 30 and 60 percent of their soil organic matter. How do you get that back?” By replacing annual crops with perennials, he says, carbon, over time, can be re-sequestered. “Over decades, it should be possible to approach where the ecosystem was to begin with, as long as the soil had not been too degraded from annual cropping,” says Crews.
SOURCE: Oxford Academic